The overall goals of this project is to optimize benefit by a cochlear implant for a deaf individual. Specific aims are to: 1) evaluate possible preoperative predictors of postoperative performance, 2) evaluate alternative sound processing strategies, 3) evaluate long-term benefit which cochlear implants, and 4) evaluate retest reliability and stability of performance measures. Postlinguistically and pre/perilinguistically deaf adults will participate in experiments to evaluate these four aims. 1) Four possible preoperative predictors of postoperative speech perception will be evaluated: gap detection thresholds for 100 Hz markers at soft and loud levels, pitch discrimination for 50/100, 50/200 and 100/200 Hz pairs (with loudness equalization), adaptation for a 100-Hz square wave, and forward masking with a 300-ms, 100 Hz masker at soft and loud levels, and a 40 ms signal at 50, 75, 150 and 200 Hz. Speech tests will include recorded nonsense syllables, words, and sentences and live-voice speech tracking presented sound-only, speechreading+sound, and speechreading only. Correlation coefficients and standard error of estimate will be used to evaluate the feasibility of prediction of postoperative speech perception. Separate analyses will be made for postlinguistically and pre/perilinguistically deaf subjects. 2) Sound processing strategies, such as multi-channel, sequential, interleaved pulses, will be compared with the standard feature extraction strategy of the Nucleus device. In addition, processing parameters, such as pairing of electrodes and assigning frequency boundaries to electrodes, will be varied and their effect on speech perception analyzed to determine what settings are associated with best performance. 3) Long-term benefit to speech perception and stability of electrical thresholds, maximum acceptable levels and sound-field thresholds will be evaluated at 3 months, 6 months, 12 months and yearly thereafter. 4) Retest reliability of the measures used in experiment 3 will be evaluated on two days within one week; stability of these measures will be evaluated one and three months later. Measurement error associated with each test will be estimated. As sufficient supporting data is obtained from these experiments, clinically efficient tests will be developed to accomplish the specific aims.